Method of flame machining



July 26,1938. W. J. JACOBSSON ET AL 2,125,182

. METHOD OF F A Patented July 26, 1938 UNITED STATES PATENT OFFICE 2,125,182 METHOD or FLAME MACHINING Application December 4, 1934, Serial No. 756,000

Renewed April 23, 1938 1 14 Claims.

at the edges of plates or other structural shapes which are subsequently united by welding. Such 15 cuts or bevels may take the shape of a half U so that, when two plates having such cuts are arranged with the beveled edges adjacent to each other, a U-shaped groove is provided that is suitable for welding.

Ordinarily there is a' tendency for fin material to remain at the edges of a cut. The formation of these fins is due to the washing effect of the slag as it is forced out of a cut and over the surface of the metallic body by the force of the oxidizing gas stream. The slag may comprise both oxidized metal and fused or molten metal, and the latter has a tendency to freeze on the sides of a cut and is exceedingly difllcult to remove.

In order to provide cuts of the character above described, which are smooth and of uniform shape with substantially no fin material formed at the edges of a out, we provide an improved method of flame machining whereby an oxidizing gas stream is progressively applied on successive surface portions, the axis of the oxidizing gas stream being at an acute angle to the surface and inclined in a direction away from an uncut portion of the surface. Preferably the oxidizing 40 gas stream is applied on the lower portion of the edge surface of a substantially horizontal metal lic plate, the oxidizing gas stream being slightly inclined downwardly and at an acute angle to.

the edge surface in the direction of the successive surface portions from which metal is to be removed, and relatively moving the gas stream and the surface. By inclining the oxidizing gas stream away from the uncut portion of the edge surface, all of the slag is effectively swept sideways of the cut and off the newly exposed surface that is produced.

The present method may be eifectively carried out in practice in the manner shown in the accompanying drawing, in which:

55 Fig. 1 is a sectional view, taken at line |-I of Fig. 2, to illustrate the relative position of a nozzle with respect to the edge of a metallic plate from which metal is removed to produce a half U-shaped cut;

Fig. 2 is a side view of the nozzle and plate shown in Fig. 1 to illustrate the downward inclination of the nozzle as it is moved parallel to the edge of the plate; and

Fig. 3 is a plan view of the nozzle and plate shown in Fig.1 to illustrate the application of the oxidizing gas stream at an acute angle to the edge surface of the plate.

To remove surface metal it must be heated to an ignition or kindling temperature before the oxidizing gas stream is applied thereto. The entire metallic body may be heated to an ignition temperature, as in a furnace, or an electric are or high-temperature heating flame may be utilized to heat successive portions of the surface metal to an ignition temperature prior to the application of the oxidizing gas stream. We preferably employ a single nozzleN to provide an oxidizing gas stream and a plurality of hightemperature heating flames. The blowpipe nozzle N may have a central passage l0 for an oxidizing gas, such as oxygen or a mixture of oxygen and air, to provide an oxidizing gas stream.

A plurality of passages ll surrounding the central passage 10 may be provided for a combustible gas, such as a mixture of oxygen and acetylene, to produce heating flames to heat the metal to be removed to an ignition temperature. Nozzles of this character are described and claimed in W. S. Walker and W. J. J acobsson application, Serial No. 536,254, filed May 9, 1931.

The nozzle N may be moved relatively to the edge of the plate I! in any suitable manner. In order to produce straight cuts a self-propelled carriage is preferably used. Such a carriage may be driven on the surface of the plate l2 and guided by a rail mounted thereon, the carriage having an arm secured thereto which extends beyond the edge of the plate. On this arm may be mounted a downwardly extending bracket to which the nozzle N can be adjustably secured. Apparatus of this character is described and claimed in J. H. Bucknam and H. J. Miller application, Serial No. 1,470 filed January 12, 1935.

In order to remove surface metal according to the present method, the nozzle N is positioned at the edge surface of a substantially horizontal plate l2 so that its longitudinal axis is slightly inclined downwardly and also at an acute angle to the surface. The oxidizing gas stream discharged from the tip of the nozzle is applied adjacent the uncut portion l3 of the surface and substantially in ,the direction of the successive surface portions from ghich metal is to be removed.

- The combustible gas issuing from the passages portion ll it produces, and sweeps over the lower portion of the; heated surface to the extreme lower edge of the plate to produce the substantially straight portion l5 of the cut, which is at an acute angle to the uncut portion l3 at the edge of the' plate, as shown in Fig. 1. f

This burning or oxidation of surface {metal just described takes place progressively as each successive portion'of heated surfaige metal comes in contact with the oxidizing gas stream: By producing a cut in this nrfanner at the vertical edge of the plate 52 with 'the oxidizing gas stream slightly inclined downwardly and away from the uncut; portion cf the edge surface, the metal removed is effectively carried away so that the newlyf exposed surface produced is exceptionally oxidizing gas? used by removing a substantial portion of the surface withegut completely oxi-- dizing it. The metal removed comprising a mixture of oxidized meta; and molten metal has been termed a slag; and such slag blown ahead'of or sidewaysjof a cut as it is being made, is reduced substantially to a non-adherent granular state. n

Since the oxidizing gas stream preferably is applied directly and progressively to the initially ex gsed substantially vertical edge surface be-' tween the upper and lower margins of said sur face and downwardly obliquely across the remainder of said surface, said stream does not attack or affect the portion iii of the initially exposed edge surface but leaves the portion l3 intact and removes surface metal only between the: portion l3 and the lower margin of the edge surface, thus providing an edge suitably shaped and prepared for welding the same to a similarly shaped edge. a

Flame machining according to the above described method has; been successfully carried out in practice with'oxidizing gas velocities ranging from 200 th 1,000 feet per second. In most applications, however, the pressure of the oxidizing gas is adjusted to produce an oxidizing gas stream having a velocity between 550 and 750 feet per'second. The velocities offthe oxidizing gas stream just givenareJhe calculated velocities of the gas discharged from. the nozzles, based on the assumption that a measured quantity or gas discharged in a given time has a temperature of 70 F. and is at atmospheric pressure.

The present method of flame machining is particularly useful in preparing the edges of relativeh thick metal plates for welding. The

finished surface, flame machined as described, carries a very thin coating of iron oxides after the loose magnetic oxide has been removed from the surface. The thickness of this iron oxide film is substantially equal to a wave length at light land beneath such oxide film there is a thin layer 'of metal containing carbon in an amount greater than that of the original metal before the'flame machining operation. Inthis manner the flame machined surface islso conditioned and improved that subsequent welding of two plates having such surfaces is considerably facilitated,

and the resulting welded joint has a strength and uniformity superior to joints heretofore produced in this field of welding.

The shape of the cut produced is dependent upon the velocity of the oxidizing gas stream and its rate of movement with respect to the surface of a metallic body, and theparticular angle at which the gas stream is applied on the surface. Generally the velocity of the gas stream and its rate of moyement with respect to the surface are selected; to obtain maximum gas economy. By varyingthe angle at which the gas stream is applied on the surface, cuts having a predetermined sectional contour can be produced." v It will therefore be understood that the present method of flame machining is not limited to the particular shaped cut illustrated and described herein. I

We claim:

1. A method of flame machining in which metal atan ignition temperature is removed from the lower portion of a substantially vertical: and initially exposed surface of ametallic body, such metal being removed to produce a cut having one edge thereof sloping inward and downward from an uncut portion of said surface, which comprises directing against said surface adjacent the uncut portion thereof a relatively low-velocity largevolume oxidizing gas stream inclined downwardly across and at an acute angle lengthwise of said surface; said stream being directed toward the successive surface portions from which metal. is to bremoved; and applying said gas stream progressively against successive portions of said surface. i

2. A method of removing metal from a substantially vertical and initially exposed surface of a metallic body to produce a out having one edge thereof sloping inward from an uncut portion of said surface, such cut extending to the extreme ipwer edge of said body,'which comprises applying at least one heating flame against said surface to heat the same to an ignition temperaturey applying against said heated surface adjacent the uncut portion thereof a relatively low-velocity large-volume oxidizing gas stream inclined downwardly across and at an acute angle lengthwise of said surface; said stream being directed toward the successive surface portions from which metal is to be removed; and relatively moving said oxidizing gas stream and the metallic body; said oxidizing gas stream having sufiicient velocity to at least partially oxidize successive portions of the surface metal at an ignition temperature and blow the same, in the form of a slag, ahead of said oxidizing gas stream and off the newly exposed surface produced.

3. A method of removing metal from a substantially vertical and initially exposed surface of a metallic body to produce a cut sloping inward from an uncut portion of said surface and extending to the extreme lower edge of said body, which comprises applying a gaseous heating flame on I 2,125, 182 such surface metal to heat the same to a temperature at which it will ignite when an oxidizing stream is applied thereon; applying on said heated surface adjacent the uncut portion thereof a relatively low-velocity large-volume oxidizing gas a and relatively moving said heating flame and said gas stream with respect to said surface.

4. A method of removing metal at an ignition temperature from a substantially vertical and initially exposed surface of a metallic body to produce a cut sloping inward from an uncut portion of said surface and extending to the extreme lower edge of said body, which comprises applying against said surface adjacent the uncut portion thereof an oxidizing gas stream having a velocity of between 200 and 1,000 feet per second; and relatively moving said gas stream and said surface; said gas stream being inclined downwardly across and at an acute angle lengthwise of said surface, and directed toward the successive surface portions from which metal is to be removed during such relative movement.

5. A method of preparing a plate or other structural shape for welding by removing surface metal at an ignition temperature from a portion of an initially exposed edge surface to produce a cut sloping inward from an uncut portion of said surface and extending to an extreme edge of said plate, which comprises directing a relatively low-velocity large-volume oxidizing gas stream downwardly across and at an acute angle lengthwise of said surface and in the direction of the successive surface portionsv from which metal is l to be removed; and progressively applying said oxidizing gas stream across successive portions of said surface so that the removed metal is blown ahead of and sideways of the cut as it is being made.

6. A method of preparing a plate or other structural shape for welding by removing surface metal at an ignition temperature from a portion of an initially exposed edge surface to produce a cut sloping inward from an uncut portion of said surface and extending to an extreme edge of said plate, which comprises progressively applying against and transversely of successive portions of such surface an oxidizing gas stream having a velocity between 200 and 1,000 feet per second, said oxidizing gas stream being applied at an acute angle lengthwise of said surface and directed toward the successive portions from which metal is to be removed so as to blow the metal removed ahead of and sideways of the cut as it face portions from which metal is to be removed.

8. A method of providing a predetermined sectional contour along an initially exposed edge surface of a metal plate which comprises sup porting said plate in a substantially horizontal position; and simultaneously and progressively applying to and downwardly across said edge sur face kindling heat and a relatively low-velocity large-volume oxidizing gas stream, said oxidizing gas stream being applied below the top surface of said plate, positioned at an acute angle lengthwise of said edge surface, and directed toward the successive surface portions from which metal is to be removed so as to undercut said plate and leave an uncut portion of said edge surface adjacent to the top surface of said plate.

9. A method of preparing an exposed edge of a metal plate or shape for welding which comprises applying a relatively low-velocity large-volume oxidizing gas stream directly to successive portions of the surface of said edge between the margins of said surface while such portions are at an ignition temperature, said stream being inclined relatively to the plane of said surface and also inclined relatively to the margins of said surface, whereby said stream does not attack aportion of the original surface of said edge adjacent one margin thereof but flows across said surface and removes surface metal from the remainder of said edge to the other margin of said surface.

10. A method of removing surface metal from an exposed surface of a metal plate or shape which comprises applying a relatively low-velocity large-volume oxidizing gas stream directly against successive portions of said surface between the margins thereof while such portions are at an ignition temperature, said stream being applied at an acute angle lengthwise of said surface at a distance from one of said margins and obliquely across the remainder of said surface and the other of said margins, whereby a portion of said exposed surface remains intact and metal is removed from the remainder of said surface.

11. A method of preparing an initially exposed edge of a plate or shape for welding which comprises applying a relatively low-velocity largevolume oxidizing gas stream directly to successive portions of the surface of said edge between the margins of said surface while such portions are at an ignition temperature, said stream being applied at an acute angle lengthwise of said surface at a distance from one of said margins and obliquely across the remainder of said surface and the other of said margins, whereby a portion of said surface remains intact and metal is removed from the remainder of said surface.

12. A method of preparing an initially exposed edge of a plate or shape for welding which comprises disposing said edge in a substantially vertical position, and applying a relatively low- .velocity large-volume oxidizing gas stream directly against successive portions of the surface of said edge below the upper margin of said surface and throughout the entire length of said plate while such portions are at an ignition temperature, said stream being applied at an acute angle lengthwise of said surface and downwardly obliquely across the remainder of said surface and the lower margin thereof, whereby a portion of such initially exposed edge surface adjacent the upper margin remains intact and metal is removed from the remainder of said surface, the thickness ofsuch removed metal increasing toward said lower margin.

13. A method of preparing the edge of a metal plate for welding which comprises progressively and concurrently advancing a high-temperature heating flame and a relatively low-velocity oxidizing jet longitudinally of said edge throughout the entire length of said plate while applying said flame and said jet obliquely against said edge along a path below the upper face of said plate and also downwardly toward the lower margin of said edge, whereby an initial portion of said edge remains intact and metal is progressively removed from a portion of said edge between such I intact portion and said lower margin.

14. A method of preparing metal plates and the like for welding which comprises concurrently moving a high-temperature heating flame and a relatively low-velocity oxidizing jet longitudi- 

